21354531 has 32 divisors (see below), whose sum is σ = 32313600. Its totient is φ = 12432000.

The previous prime is 21354451. The next prime is 21354551. The reversal of 21354531 is 13545312.

It is not a de Polignac number, because 21354531 - 2⁹ = 21354019 is a prime.

It is a super-2 number, since 2×21354531² = 912031988459922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21354551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 143245 + ... + 143393.

It is an arithmetic number, because the mean of its divisors is an integer number (1009800).

Almost surely, 2^21354531 is an apocalyptic number.

21354531 is a deficient number, since it is larger than the sum of its proper divisors (10959069).

21354531 is a wasteful number, since it uses less digits than its factorization.

21354531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 307.

The product of its digits is 1800, while the sum is 24.

The square root of 21354531 is about 4621.0962984989. The cubic root of 21354531 is about 277.4363395890.

Adding to 21354531 its reverse (13545312), we get a palindrome (34899843).

It can be divided in two parts, 2135 and 4531, that added together give a palindrome (6666).

The spelling of 21354531 in words is "twenty-one million, three hundred fifty-four thousand, five hundred thirty-one".